Rotational Technologies for Space Infrastructure

ABSTRACT

A spacecraft refueling and storage system comprising a first tank and a second tank for storing propellant, a rotatable shaft to which the first and second tanks are mounted for rotating the first and second tanks about an axis of the shaft, and a drive motor for rotating the shaft so that upon rotation of the first and second tanks, liquid propellant is separated from gas in the propellant and settled to an outer portion of the first and second tanks.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit under 35 U.S.C. § 119 to U.S.provisional application No. 63/123,946 filed Dec. 10, 2020, the entiretyof which is hereby incorporated by reference.

FIELD OF USE

This present invention relates generally to rotational technologies forspace infrastructure including, for example, a spacecraft on-orbitadvanced refueling system (SOARS), and more particularly a device andmethod for storing and transferring fluid/propellant in low, high orzero gravity environments.

BACKGROUND

Space vehicles traveling beyond low earth orbit (LEO) require largeamounts of liquid propellant not only to escape the gravitational pullof the Earth, but also to position the spacecraft in geosynchronous andtransfer orbits. Orbiting propellant depots can extend the life andmission profile of space vehicles. However, in microgravity conditions,propellants inside the tank are dispersed randomly, and it can bedifficult to predict their behavior. Also, the chaotic nature of fluidbehavior in reduced gravity environments limit the assessment andmanagement of space fluids for extraterrestrial applications. In-spacerefueling from an orbiting propellant depot can be used to extend therange and mission capabilities of these space vehicles. However, currentin-space propellant transfer methods rely on expensive and heavy pumpsand diaphragms that do not provide sufficient high transfer efficiencyor reliability. These methods that rely on heavy pumps and pressurizedinert gases are prone to accelerated boil-off and do not maintainpropellant in usable and sustainable conditions long-term. Also, thesemethods require significant resources for liquid acquisition and utilizefault-prone components. Further, these methods require a separate supplyof stored gases to generate high pressures for fluid separation. Inaddition, in microgravity conditions, propellants inside the tank aredispersed randomly, and it can be difficult to predict their behavior.Utilization of cryogenic resources is further limited by advancedthermal and structural operating requirements.

SUMMARY

There is a need for fluid management systems for space depot platformsthat can maintain propellant in usable and sustainable conditions inreduced gravity environments in order to support the growing demand forLEO, cislunar and deep space exploration capabilities.

At least one embodiment of the storage system disclosed herein comprisesa first tank and a second tank for storing propellant, a rotatable shaftto which the first and second tanks are mounted for rotating the firstand second tanks about an axis of the shaft, a drive motor for rotatingthe shaft so that upon rotation of the first and second tanks, liquidpropellant is separated from gas in the propellant and settled to anouter portion of the first and second tanks, a first flow path formed inthe shaft, a second and third flow path for transferring the settledliquid in the first tank and the second tank, respectively, to the firstflow path, and a fourth flow path for transferring fluid from the firstflow path to the spacecraft.

These and other features and advantages will be apparent from a readingof the following detailed description and a review of the associateddrawings. It is to be understood that both the foregoing generaldescription and the following detailed description are explanatory onlyand are not restrictive of aspects as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The invention will be more fully understood by reference to the detaileddescription, in conjunction with the following figures, wherein:

FIG. 1 shows the systems and subsystems of one embodiment of aspacecraft on-orbit advanced refueling system (SOARS) of the presentinvention.

FIGS. 2A and 2B show schematic views of a device and system for storingand transferring fluid/propellant.

FIG. 3 shows one possible arrangement for a SOARS operation.

FIG. 4 shows one possible arrangement for the device for storing andtransferring fluid/propellant.

FIGS. 5A and 5B show how the fluid from the rotating tanks housed in theESPA standard ring shown in FIG. 4 is transferred to the receiving tanksof the astrobees/spacecraft.

FIG. 5C shows one possible arrangement of a schematic view of the deviceof FIG. 4 .

FIGS. 6A and 6B show three-dimensional views of an embodiment of theinvention.

FIG. 7 shows some of the phases of operation of the transfer of fluidfrom the rotating tanks of the SOARS.

FIG. 8 shows another embodiment of the depot tank.

FIGS. 9A-9C show additional embodiments of the depot tanks.

FIG. 10 shows how a microcontroller can be configured to control theoperation of the SOARS.

DETAILED DESCRIPTION

The subject innovation is now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerals specific details are set forth in order to provide a thoroughunderstanding of the present invention. It may be evident, however, thatthe present invention may be practiced without these specific details.

FIG. 1 shows the systems and subsystems of one embodiment of aspacecraft on-orbit advanced refueling system (SOARS) of the presentinvention. Payload Systems can encompass technologies and mechanismsthat drive depot kinematics and transfer dynamics. Bus Systems caninclude depot infrastructure and communications that support and operatePayload Systems. The SOARS Dynamics & Control Subsystem (DC S) can beused to initiate, control, and stabilize depot kinematics duringoperation. Propellant settling prior to transfer can be driven bythruster mechanisms to spin the system up-to-speed. During spin-up andtransfer, the DCS can use thrusters to mitigate propellant slosh effectsand settling instabilities that may emerge. If the depot configurationrequires, a moving mass system can be incorporated into the DCS inintegration to thrusters that can provide baseline shifts in system CGand trim instabilities. Attitude and (re-)orientation operations of thedepot can be executed using existing thruster and moving mass mechanismsto maintain stability during obstacle avoidance and non-cooperativeclient maneuvers.

The SOARS Propellant Transfer Subsystem (PTS) can provide reliable andefficient propellant management during depot-client transfer operations.Pressure controllers and necessary valves, pressure regulators, andflowrate sensors can be used to establish and maintain necessarypressures to initiate transfer and regulate mass flow rate. Propellantpiping geometry and material selection can reduce transfer path lengthand ensure thermochemical compatibility with target propellant (i.e.liquid hydrogen, liquid oxygen, liquid methane, hydrazine). The SOARSClient Docking System (CDS) can support client agnostic berthing anddepot-client mating during transfer/maintenance operations. Upon clientapproach, robotic mechanisms (i.e., robotic arms, autonomous tethers,etc.) can be utilized to guide the client to the target propellanttransfer port. Prototype CDS can incorporate quick connect anddisconnect adapters (QC/QD) to minimize client operations duringdocking. Adapter construction or selection can take into account thermaland fluid characteristics of the operating propellant and clientpropellant tank configuration. If the client does not have SOARS QC/QDadapters (e.g., legacy satellites in LEO), on-depot tooling and roboticmechanisms can be used to access the propellant tanks.

The SOARS Cryogenic Storage System (CSS) can enable long-durationstorage of cryogenic propellants for client servicing. Passivecomponents, such as cryogenic insulative materials and shieldingstructures, can be used to maintain thermal requirements. For activereestablishment of cryogenic fluids, the SOARS system can incorporatecryocooling and boil-off mitigation subsystems. The SOARS CommunicationSystem (CS) can execute data transfers for depot-to-client anddepot-to-ground communications. Client-facing data can be used to enableassessment of propellant transfer status during operation, includingalerting by fault detection systems. Over the lifetime of depotoperation, ground-based communications may be required to monitor SOARShealth and provide timely maintenance and repairs.

The SOARS On-Board Computer (OBC) can manage general depot maintenanceand operation signaling—balancing navigation, fault detection, sensorfusion, and data analytics. Though the DCS can drive depot rotation andstabilization actuation, the OBC can execute navigation, attitude, andpositioning of the depot to ensure proper orbital mechanics.Operation-related health monitoring, usage logging, and fault detectioncan be catalogued, and necessary responses to depot-client state changescan be managed via the OBC. Sensor data collected during operation canbe fused intelligently to provide actionable insights for autonomousdepot response and ground-crew decision making.

The SOARS Electrical & Power System (EPS) can serve to provide primarypower to depot sensors-actuators through the use of appropriate solarpanel arrays, batteries, and insulated electrical conduits. Full-scaleSOARS depots can provide client auxiliary power or re-chargingcapabilities using SOARS stored power. The EPS can follow safetystandards to mitigate the risk of electrical fires or spark-generationin the event of EPS damage. A SOARS Structural & Thermal System (STS)can be used to structurally support the depot subsystems and providethermo-mechanically robust platforms, mounts and actuators to withstandthe centrifugal loading of the depot structures, thermalexpansion-shrinking and off-nominal dynamic loads generated by berthednon-cooperative clients and ensure long-durationcryogenic-compatibility.

An exemplary embodiment of is shown in FIG. 2A. Specifically, FIG. 2Ashows a schematic view of a device and system for storing andtransferring fluid/propellant in low or zero gravity environments in aSOARS. As shown in FIG. 2A, the refueling device 1 rotates the depottanks 10 and 20 about the rotational axis 30 to settle and separate thetwo-phase gas-propellant into liquid settled propellant 40 and volatilegas 50 using the centrifugal force caused by the rotation. The liquidsettled propellant 40 is transferred to the client spacecraft 70 throughtransfer lines 60. This transfer can be initiated by applying a pressuredifferential using stored gas or boil-off gases.

FIG. 2B shows another embodiment of the present invention. As shown inFIG. 2B, a drive motor 110 rotates depot tank A 120 and depot tank B 130about rotational axis 140 in order to settle and separate the two-phasegas-propellant into liquid settled propellant and volatile gas using thecentrifugal force caused by the rotation. Reference numeral 145 shows aslip ring and load cell. The slip ring can be used to connect anddeliver electrical signals (e.g., communications, data and controlsignals) and the load cell can be used to measure kineticcharacteristics (i.e., reaction forces and torques) between thecomponents, which can be used to maintain stability of the system. Thecontrol valves are used to transfer fluid between the tanks and thedifferent components of the system. Compressed gas can be used topressurize components in the system in order to drive fluid transfer todifferent components. Transfer valves 160 control the flow of liquidpropellant from depot tank A and B to client tank 170. The client tank170 can include a docking interface to couple the client tank 170 to theother components of the system shown in FIG. 2B. Flow transmitters180/190 measure the flow of propellant from the depot tanks A and B,respectively, to the client tank 170. Pressure transducers 150 measurethe pressures in depot tank A and depot tank B. Although two (2) depottanks are shown in FIG. 2B, any number of depot tanks can be used. Also,the embodiments shown in FIGS. 2A and 2B can be adaptable to orbitalvehicle-mounted and surface-mounted platforms. The embodiments show inFIGS. 2A and 2B make it possible to minimize the use of expensive andfailure-prone pumps and improve cryogen boil-off mitigation.

FIG. 3 shows one possible arrangement for a SOARS operation. As shown inFIG. 3 , a client satellite can dock with the SOARS for clientrefueling. The SOARS can be located at various orbital positions such aslow earth orbit (LEO), geosynchronous orbit (GEO), the first lagrangianpoint L1, the fourth lagrangian point L4, etc. The SOARS also can beused for lunar, Martian and asteroid missions.

FIG. 4 shows the device for storing and transferring fluid/propellant ofFIGS. 2A and 2B mounted in an ESPA standard ring or housing fortransferring the fluid/propellant to a receiving tank mounted on anastrobee. The astrobees can be used to maintain stability duringtransfer. Air pressure can be used to transfer the fluid to theastrobees. Any type of spacecraft also can be used in place of theastrobees shown in the figures. Also, the astrobees could be replacedwith thrusters or use the clients' thrust mechanisms to stabilize thesystem. The ESPA standard ring can include any number of docking ports,which can be self-aligning docking ports, that can be used to dockmultiple astrobees or spacecraft to the ESPA standard ring forrefueling. The tank configuration of the system can be modular and canbe scaled to a larger number of tanks and and/or larger tanks. Also, theorientation and size of the system tanks can be configured to ensurerotational stability across all fluid distributions.

FIGS. 5A and 5B show how the fluid from the rotating tanks housed in theESPA standard ring shown in FIG. 4 is transferred to the receiving tanksof the astrobees/spacecraft. As shown in FIGS. 5A and 5B, the rotatingtanks rotate about a shaft 310. First, the fluid that has settled in theoutside portion of the tanks due to the rotation is transferred throughflow paths 410 to a center hub formed in the shaft 310. Then, as shownin FIG. 5B, the fluid is transferred through a pathway 420 formed in theshaft 310 to a position below the rotating tanks, and then to thereceiving tanks of the astrobee/spacecraft through flow path 430 formedoutside of the rotating tanks. The transfer of the fluid through theflow paths can be initiated by applying a depot-client pressuredifferential using stored gas or boil-off gases.

The shaft 310 can also include a rotary union and a slip ring integratedinto the shaft 310 that allows fluid and electrical transfer between therotating tanks and the shaft 310. For testing purposes, water can beused, but in operation in space, any liquid such as liquid propellant ora biological sample can be used. The flow paths can be made using NPTand/or NPTF plated brass fittings with high pressure push-to-connectseals, but any other fittings and connections could be used based onfluid handling requirements. Check valves can be placed along the flowpaths to control the flow of fluid therethrough.

FIG. 6A shows a three-dimensional view of the rotating tanks housed in aframe 510 of one embodiment of the invention. A rotary union, slip ringand bearing 520 are positioned in a housing 530 formed on a top plate540 of the housing 510. A motor 550 that drives the rotating tanks isalso formed on the top plate 540. FIG. 6B shows one of the rotatingtanks of FIG. 6A. As shown in FIG. 6B, the tank, the rotating tanks caninclude a camera system for monitoring and assessing internal massdistribution in the system. For example, machine vision (e.g., objectrecognition, density estimation, and volume estimation) can be used toassess the distribution of fluids and solids in the tank, which can befed into a system inertia model that can predict instability usingsensed kinematic and kinetic data to drive corrective actions. Amono/stereo/multi-camera system can be included as a measurementmodality. The system shown in FIG. 6B also can include a flowmeter formeasuring flow through the flow paths, solenoid valves along the flowpaths for opening and closing the flow paths to allow liquid transferand enable target pressurization, pressure sensors, drain ports,fill/vent ports and flow instrumentation unit.

In the system of FIGS. 6A and 6B, a brushless DC motor, for example a 15W 1/50 HP motor with a belt-driven aluminum shaft, could be used tocreate an angular velocity of 60 rpm for the rotating tanks. A motordriver can be used to limit torque output and define acceleration times.For the flowmeters, a Bell Systems 10-1000 mL/min oval gear microflowmeter can be used. For the pressure sensors, Omega stainless steel 0-30psi pressure sensors can be used. The tanks can be made ofdouble-contained (nested) acrylic or polycarbonate of an appropriatethickness of approximately ⅛″, for example. The tanks can beindependently face-sealed with silicone or grease against aluminum caps.

FIG. 7 shows some of the phases of operation of the transfer of fluidfrom the rotating tanks of the SOARS to the astrobees. In FIG. 7 , theterm “astrobees” is used, but the operation can be used for any type ofspace vehicles, clients or recipients. One or more astrobees can bepre-docked to stabilize the ESPA ring before the docking maneuver isconducted. In Phase 1, docking of the astrobee identifies the AR(augmented reality) tag of the SOARS docking port and maneuvers intoalignment with the SOARS port. The AR tags allow the astrobee toidentify the docking port and maneuver to the target. The AR tags, whichare shown schematically in FIG. 5C, can contain various types ofinformation of the docking port such as the type of docking interface,structural characteristics, pressure characteristics, the type ofpropellant/liquid that is provided at the docking port, operatingpressures, etc. Other types of alignment tags can be used, such as QR(Quick Response) tags, RFID tags, etc. The astrobees can use internalsensors and controls for position-holding SOARS during operation. Then,the astrobee contacts the docking interface and the SOARS triggers thelatching of the docking interface, tightens contact and seals thetransfer lines. Servo-driven latching mechanisms and electrical contactscan be used within the docking interface to assist with the latching.Also, a multi-point circuit closure detector can be used within thedocking interface to verify successful latching. In Phase 2, the SOARSspins up to a target angular velocity. In Phase 3, the air pumps turnon, pressure control solenoid valves (PCSV's) open to allow forpressurization. Once pressurized, flow transfer solenoid valves (FTSV's)open to allow liquid flow. Self-sealing ports for liquid and air allowfor transfer between SOARS and the astrobee tanks. The PCSV's then canopen and close to maintain a target pressure differential between theSOARS and astrobee tanks. Phases 1-3 can then be repeated with differentoperating parameters, such as different pressures, different angularvelocities and different tank fills. The electronics enclosure shown inFIG. 5C can include microcontrollers, sensors, drivers, actuators andother electronics. Any type of a suitable microcontroller can be usedsuch as two (2) teensy 4.1 Arduino-based microcontrollers. Themicrocontroller can be configured to execute software code to controlthe operation of the SOARS such as the rotational rate of the rotatingtanks, tank pressures, and flow actuation. This software codearchitecture shown in FIG. 10 can be comprised of algorithmic modules tostructure and store real-time system data, perceive system state, decidestate change, and execute commands to maintain stable operation. Thealgorithmic modules, in their entirety or sub-section, can include someor all of the following module features: multi-modal data structuringand fusion, system and environment perception for machine situationalawareness, system-environment state prediction and state changedecision-making, and corrective action command and execution. Dataingestion and signal conditioning through the Sensor Interface pullsfrom multi-modal data streams (i.e., use cameras, pressures, flows,accelerations, torques). Structured data is stored in System Memory fordownstream predictive functions and train leaning algorithms. Structureddata is also passed downstream to the Perception Module, which cancomprise of a system dynamics estimator to derive system-environmentintrinsic and extrinsic parameters (i.e., system inertia, massdistribution, instability mode), and system and environment stateclassifiers to classify the system state based on sensor input andestimated derived parameters. The Decision Module takes in dynamics andstate data to predict future system state using current classificationand data streams, and to estimate the total system and environment statedeviation across multi-dimensional target dynamics-state criteria. TheCommand Module takes in dynamics-state deviation data, in coordinationwith actuator and end-effector models (i.e., models of systemcomponents, such as thrusters, actuators, valves) and system reactionprediction models, to identify optimal corrective actions (e.g.,pressurize, start transfer, change system attitude), to return systemoperation within target dynamics-states (e.g., mitigate instability,maintain state, or change state). All data and actions from thesemodules are tracked and stored in System Memory for training andoptimization of learning algorithms within each module. Any or allsystem dynamics-state modules and algorithms may incorporate anycombination of physics-based, heuristics-based, or empiricallylearned-trained real-time algorithmic models (e.g., neural networks).Modules and sections of this code may or may not be run simultaneously,in the background across multi-processor computer systems, and orsequentially in a reactive manner. Also, the electronics enclosure caninclude an on-board battery to supplement the astrobee batteries and/orother electrical systems.

FIG. 8 shows an embodiment of a depot tank 800 that contains a liquidand a gas. As described above, the depot tank 800 is rotated about ashaft to induce the liquid to move towards the outer portion (left side)of the tank 800 and induce the gas to move towards the inner portion(left side) of the tank 800. Baffles are formed inside the tank 800 tohelp guide the liquid towards the outer portion of the tank 800 and thegas towards the inner portion of the tank 800 where they are collectedand processed. As shown in FIG. 8 , the depot tank 800 includes internalbaffles 810 that can be used to channel/guide the fluid to the outerportion of the tank 800. The baffles can form converging sections thathelp move the liquid further outward and the gas further inward.Openings 820 can be formed in the baffles through which the liquid andgas travel to the outer and inner portion of the tank, respectively.These openings can be one-way devices 830, pass-through orifices,controlled flow channels that induce the desired flow regime. Dependingon the fluid being stored and transferred, the openings can reduce flow,maintain pressure differential across the baffle, or manipulate thefluid characteristics (e.g., temperature, liquid-gas state change,density, etc.) in a one-way flow manner. A transfer flow path 840connects the outer portion of the tank 800 to transfer the liquid to aspacecraft 850. The baffles can incorporate vanes or surface patterningof various dimensions and configurations to control flow regimes of thebulk fluid and the wall boundary layer. Also, vanes can be used induceor stabilize flow turbulence for adjusting flow parameters (e.g.,pressure, flow rate, bulk density, etc.) prior to flowing into desiredregions of tank or across a baffle. Micropatterning having boundarylayers can be used to control or reduce wall shear loads or adjustfree-surface energy of the fluid-wall interface to drive desired flowregime. Thermal control or actuation (e.g., electromagnetic, mechanical,etc.) of the baffle may also be used to perturb or induce desired flowacross or through the baffle. The material used for the baffles can beselected based on fluid storage and flow requirements. The exactconfiguration (size, number, orientation, instrumentation, actuation,temperature, and material composition, etc.) of the baffles can be setbased on the fluid storage and flow requirements.

FIGS. 9A-9C shows additional embodiments of the depot tanks. As shown inFIG. 9A-9C, the depot tanks can be arranged in different configurations,all within the scope of the present invention. For example, inadditional to the axial arrangement for two (2) tanks shown in FIG. 9A,the tanks could be arranged circumferentially as one tank, as shown inFIG. 9B. Alternatively, three (3) tanks can be used arranged toroidallyas shown in FIG. 9C. In all of these embodiments, different sizes,shapes and materials can be used.

It should be understood that the invention is not limited by thespecific embodiments described herein, which are offered by way ofexample and not by way of limitation. Variations and modifications ofthe above-described embodiments and its various aspects will be apparentto one skilled in the art and fall within the scope of the invention, asset forth in the following claims. For example, various materials,dimensions, fasteners, and connections could be used in the stairway andplatform system without departing from the scope of the invention.

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 10. (canceled) 11.A spacecraft refueling and storage system comprising: a first tank and asecond tank for storing propellant; a rotatable shaft to which the firstand second tanks are mounted for rotating the first and second tanksabout an axis of the shaft; and a drive motor for rotating the shaft sothat upon rotation of the first and second tanks, liquid propellant isseparated from gas in the propellant and settled to an outer portion ofthe first and second tanks.
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 20. The spacecraft refueling and storage system of claim 11,further comprising a moving mass system that provides shifts in thecenter of mass of the system in order to stabilize system kinematics.21. The spacecraft refueling and storage system of claim 11, furthercomprising a moving mass system that performs attitude andre-orientation operations.